Net::IMAP implements Internet Message Access Protocol (IMAP) client functionality in Ruby. From versions 0.4.0 to before 0.4.24, 0.5.0 to before 0.5.14, and 0.6.0 to before 0.6.4, when authenticating a connection with SCRAM-SHA1 or SCRAM-SHA256, a hostile server can perform a computational denial-of-service attack on the client process by sending a big iteration count value. This issue has been patched in versions 0.4.24, 0.5.14, and 0.6.4.

Attack Vector Network

Attack Complexity Low

Privileges Required None

Attack Requirements Present

User Interaction Passive

Vulnerable System Confidentiality Impact None

Vulnerable System Integrity Impact None

Vulnerable System Availability Impact High

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact High

User Interaction Required

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

The EPSS score is 0.00046.

Exploitation none

Automatable no

Technical Impact partial

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
ruby net-imap affected
Version Status Constraints
>= 0.4.0, < 0.4.24 affected —
>= 0.5.0, < 0.5.14 affected —
>= 0.6.0, < 0.6.4 affected —

Configuration 1 [-]

OR cpe:2.3:a:ruby-lang:net\:\:imap:*:*:*:*:*:ruby:*:*
cpe:2.3:a:ruby-lang:net\:\:imap:*:*:*:*:*:ruby:*:*
cpe:2.3:a:ruby-lang:net\:\:imap:*:*:*:*:*:ruby:*:*

No data.

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Vendors Products
Ruby-lang Subscribe
Net::imap Subscribe

Project Subscriptions

Vendors Products
Ruby-lang Subscribe
Net::imap Subscribe
Net\ Subscribe
Advisories
Source ID Title
Github GHSA Github GHSA GHSA-87pf-fpwv-p7m7 net-imap vulnerable to denial of service via high iteration count for `SCRAM-*` authentication
Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://github.com/ruby/net-imap/commit/158d0b505074397cdb5ceb58935e42dd2bcfa612 cve-icon cve-icon cve-icon
https://github.com/ruby/net-imap/commit/808001bc45c06f7297a7e96d341279e041a7f7f4 cve-icon cve-icon cve-icon
https://github.com/ruby/net-imap/commit/99f59eab6064955a23debd95410263ad144df758 cve-icon cve-icon cve-icon
https://github.com/ruby/net-imap/releases/tag/v0.4.24 cve-icon cve-icon cve-icon
https://github.com/ruby/net-imap/releases/tag/v0.5.14 cve-icon cve-icon cve-icon
https://github.com/ruby/net-imap/releases/tag/v0.6.4 cve-icon cve-icon cve-icon
https://github.com/ruby/net-imap/security/advisories/GHSA-87pf-fpwv-p7m7 cve-icon cve-icon cve-icon
https://nvd.nist.gov/vuln/detail/CVE-2026-42256 cve-icon
https://www.cve.org/CVERecord?id=CVE-2026-42256 cve-icon
History

Mon, 18 May 2026 18:15:00 +0000

Type Values Removed Values Added
First Time appeared Ruby-lang net\
CPEs cpe:2.3:a:ruby-lang:net\:\:imap:*:*:*:*:*:ruby:*:*
Vendors & Products Ruby-lang net\

Sat, 16 May 2026 00:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-606
References
Metrics threat_severity

None

 cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H'}

threat_severity

Moderate

Mon, 11 May 2026 17:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Sun, 10 May 2026 20:15:00 +0000

Type Values Removed Values Added
First Time appeared Ruby-lang
Ruby-lang net::imap
Vendors & Products Ruby-lang
Ruby-lang net::imap

Sat, 09 May 2026 20:00:00 +0000

Type Values Removed Values Added
Description Net::IMAP implements Internet Message Access Protocol (IMAP) client functionality in Ruby. From versions 0.4.0 to before 0.4.24, 0.5.0 to before 0.5.14, and 0.6.0 to before 0.6.4, when authenticating a connection with SCRAM-SHA1 or SCRAM-SHA256, a hostile server can perform a computational denial-of-service attack on the client process by sending a big iteration count value. This issue has been patched in versions 0.4.24, 0.5.14, and 0.6.4.
Title net-imap: Denial of service via high iteration count for `SCRAM-*` authentication
Weaknesses CWE-1322
CWE-770
References
Metrics cvssV4_0

{'score': 6, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-05-11T17:04:42.562Z

Reserved: 2026-04-26T11:53:27.704Z

Link: CVE-2026-42256

cve-icon Vulnrichment

Updated: 2026-05-11T17:04:36.128Z

cve-icon NVD

Status : Analyzed

Published: 2026-05-09T20:16:28.313

Modified: 2026-05-18T18:06:58.657

Link: CVE-2026-42256

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-05-09T19:38:33Z

Links: CVE-2026-42256 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-05-16T02:00:12Z

Weaknesses